Culver's famous Butter Burger is a great step up from classic fast food options like McD's or BK's, but isn't at the same level as Red Robin, In-N-Out Burger, or Five Guys'. That being said, it is still delicious, and, since there are Culber's restaurants all over Wisconsin, it's convenient.
The real reason to go to Culver's is for their custard. Concrete mixers are where it's at, and, if you're not careful, you'll move to Wisconsin 40 pounds lighter than when you move out.